Proposed inductive voltage adder based accelerator concepts for the second axis of DARHT

As participants in the Technology Options Study for the second axis of the Dual Axis Radiographic HydroTest (DARHT) facility located at Los Alamos National Laboratories, we have considered several accelerator concepts based on the inductive voltage adder (IVA) technology. The accelerator design requirements for the IVA approach include: /spl ges/12-MeV beam energy; /spl sim/60-ns electrical pulse width; /spl les/40-kA electron beam current; /spl sim/1-mm diameter e-beam; four pulses on the same axis or as close as possible to that axis; and an architecture that fits within the existing building envelope. To satisfy these requirements our IVA concepts take a modular approach. The basic idea is built upon a conservative design for eight ferromagnetically isolated 2-MV cavities that are driven by two 3 to 4-/spl Omega/ water dielectric pulse forming lines (PFLs) synchronized with laser triggered gas switches. The 100-/spl Omega/ vacuum magnetically insulated transmission line (MITL) would taper to a needle cathode that produces the electron beam(s). We narrowed our study to the following options: (A) four independent single pulse drivers powering four single pulse diodes; (B) four series adders with interleaved cavities feeding a common MITL and diode; (C) four stages of series PFLs, isolated from each other by triggered spark gap switches, with single-point feeds to a common adder, MITL, and diode; and (D) isolated PFLs with multiple-feeds to a common adder using spark gap switches in combination with saturable magnetic cores to isolate the nonenergized lines. We discuss these options in greater detail identifying the challenges and risks associated with each.